Frequently, overfilled bridges formed of precast or cast-in-place concrete are used to support one pathway over a second pathway, which can be a waterway, a traffic route or the like. The terms “overfilled arch” or “overfilled bridge” will be understood from the teaching of the present disclosure, but in general, an overfilled bridge or an overfilled arch is a bridge formed of arch elements that rest on the ground or on a foundation and has soil or the like resting thereon and thereabout to support and stabilize the bridge. The arch form is generally cylindrical in circumferential shape, and in particular a prolate shape; however, other shapes can be used. An example of an overfilled bridge is disclosed in U.S. Pat. Nos. 3,482,406 and 4,458,457, the disclosures of which are incorporated herein by reference.
Presently, reinforced concrete overfilled arches are usually constructed by one of two methods. The first method includes completing the entire arch structure in place, with formwork used to create the arch profile. This method generally requires formwork on both the inside and the outside of the arch profile as the sides of the arch are generally too steep to be cast without the support provided by formwork. Formwork on the outside of the arch may generally be omitted at the apex of the arch where the gradient of the arch shell is less than about 20° to 30° from horizontal. The provision of such outside form work is both costly and time consuming and may reduce the finished quality of the formed concrete. Furthermore if outside formwork is used, there are restrictions on the thickness of the vault, such as to ensure good quality concrete the arch vault cannot be less than roughly one foot thick.
A second common method of constructing reinforced concrete overfilled arches is to pre-cast the complete arch or arch halves in sections (elements) and to subsequently place the pre-cast elements onto prepared footings. An example of this type of construction method is disclosed in U.S. Pat. No. 3,482,406. This construction method requires construction of re-usable molds and the transport and lifting of the finished arch profiles into their permanent locations. The aforementioned re-usable mounds are a significant initial investment. This renders this method of construction uneconomical if the molds cannot be re-used to supply elements for the construction of many arch bridges. Investment in such molds is therefore made by pre-casting manufacturers and the arch elements are produced in their factories and transported to the bridge construction site. Problems associated with the transport of such arches and the requirement of a construction crane large enough to lift complete arch elements are disadvantages of this method.
Furthermore, transporting large pre-cast structures may involve complex and expensive transportation problems. Roadways, permits, escorts and clearance requirements must be accounted for, as well as traffic problems and schedules. Still further, in some constructions, very large cranes are required which further exacerbates all of the above-mentioned problems.
Therefore, there is a need for an economical and efficient overfilled bridge and method of constructing an overfilled bridge.
Pre-cast structures are not as versatile as possible, especially if unusual terrain or specifications are present. In particular, precast structures are limited in the forms of curtailment which can be applied at the ends of the bridge. Therefore, there is a need for an overfilled bridge and method of constructing an overfilled bridge that is versatile and amendable to design variations.